The major objectives of the present investigation are (1) to determine the interrelationship between early infant growth, caloric intake, and level of physical activity, as measured by the wrist watch actinometer, within a population of lower income, artificially fed infants, and (2) to determine whether there is evidence of operant conditioning/by the caretaker of infant food acceptance as a possible factor in the early pathogenesis of maladaptive feeding behavior. Initially, a one week total caloric intake determination and two 24 hour activity measurements at approximately 12 weeks of age, together with growth in length and weight from birth through 12 weeks of age will be carried out with a population of approximately 12 infant boys and 12 infant girls. This population will be studied, using an adaptation of Michael Lewis' continuous observational analysis of maternal - infant interaction to determine the extent to which social reinforcement during feeding may correlate with growth, and caloric intake at 12 weeks and with achieved growth at 12 and 24 months of age.